1. Field of the Invention:
The present invention relates to a photoresist material which contains organo-silicon groups and is suitable for forming a micropattern applied in the fabrication of semiconductor integrated circuits and magnetic bubble memory elements. It more particularly relates to a photoresist material having a high resistance to plasma etching using oxygen gas.
2. DESCRIPTION OF THE PRIOR ART
In the fabrication of integrated circuits and bubble memory elements, dry etching using a gas plasma, an ion shower, or the like has been used in place of conventional wet etching since a photoresist pattern prepared by micropatterning can be accurately transferred to a substrate. For this reason, there is a need for a photoresist material having a high resistance to dry etching.
In order to obtain a high resolution from such a photoresist material, a three-layered photoresist has been proposed by J.M. Moran et al., in J. Vac. Sci. Technol., Vol. 16, 1620, (1979). The photoresist described there consists of a lower layer of a thick organic film, an intermediate layer of a silicon layer or a silicon oxide layer, and an upper layer of a thin organic film. However, this photoresist requires a complicated and prolonged etching process which is undesirable.
If a photoresist material having a good resistance to dry etching when emplying, for example, oxygen is used, such a material would also serve as the intermediate and upper layers of the three-layered structure. Therefore, the etching process can be considerably simplified.
Typical examples of such a material are photoresist materials having silicon atoms and described in Japanese Patent Laid-Open applications (Kokai) Nos. 60-196750; 60-119550; and 59-208542.
However, these photoresist materials are sensitive to electron beams and cannot be used with g-line steppers having a wavelength of 436 mm which presently constitute the most widely used exposure apparatuses.
It is also known that a polydimethylsiloxane has excellent resistance to an oxygen plasma and an etching rate of about 20.ANG./min. However, this polymer has the drawback that since it is liquid at room temperature, the fluidity of the polymer fails to provide high resolution, and the polymer is thus unsuitable for use as a photoresist material.
A polyacetylene-based photodecomposition type positive photoresist material such as a product available from Sanyo Kasei K.K. has been proposed as a silicon-based photoresist having a g-line absorption property. However, this photoresist material does not have a sufficiently high resolution or high sensitivity since the material is developed with the use of an organic solvent, and the throughput is low. This photoresist material is thus unsuitable for practical use.